The present invention relates to x-ray imaging radiography and, more particularly, to a novel method and apparatus for photocontrolled ion-flow electron radiography.
Conventional x-ray imaging techniques, using the screen-film system, are being replaced with xeroradiography, whereby the x-rays differentially absorbed in an object being analyzed cause the deposition of an electrostatic image on an insulative sheet for development by xerographic techniques after exposure. One prior art arrangement for the electrostatic recording of x-ray images utilizes a pair of spaced electrodes with a gas-filled gap therebetween and the first electrode comprising overlayed layers of an ultraviolet-emitting fluorescent material and an air-exposable ultraviolet-sensitive photoemitting material. A plastic sheet is positioned adjacent to the other electrode and an electric field is applied across the gap to accelerate photoelectrons emitted by the photoemitting material and amplified by the gas in the gap, causing an electrostatic image to be formed on the plastic sheet before subsequent xerographic development. This device is disclosed in U.S. Pat. No. 3,940,620, issued Feb. 24, 1976 and assigned to the assignee of the present invention.
It is desirable to eliminate the amplifying gas, for reasons of extraneous noise generation. It is also desired to provide a radiographic system capable of amplifying the differential x-ray image to the greatest extent possible, whereby x-ray dosage to the patient may be reduced.